1. Field of the Invention
Embodiments of the present invention relate to automatically adjusting the light colour of emitters, and more particularly, to methods and systems for automatically adjusting light intensity of multiple emitters that collectively emit light at a predefined light-intensity.
2. Description of the Related Art
Conventional light sources that have been used since a long period of time most commonly include either incandescent or gas discharge. Currently, the utilization of regular incandescent lamps having a filament is slowly reducing. There are one or more factors for this, but the most important factor is the impact on surrounding environment. Incandescent lamps have poor energy efficiency, i.e. most of the energy fed to the filament is converted to heat. Particularly, most of the input energy of traditional lighting is wasted as heat or infrared (non-visible) light in the environment. Only about 5% of the energy produces radiation in the visible range, i.e. light. Moreover, the lifetime of the incandescent bulb is limited and when failure occurs it is disastrous. The use of normal incandescent lamps is thus reduced in favour of low energy lamps, such as halogen incandescent lamps, fluorescent lamps and also LED lamps.
Traditional fluorescent bulbs have a longer life, but have significant performance variations across a range of temperatures. At some colder temperatures fluorescent bulbs do not function at all. Halogen light sources are a slight improvement in efficiency and lifetime over incandescent light sources for a marginal increase in cost.
As it is well known, in various countries, some varieties of incandescent lamps are even banned from the market in order to force the customers to choose more energy-efficient light sources. The wavelength spectrum of regular low energy lamps, i.e. of fluorescent lamps and also LED lamps is more or less acceptable for the human eye.
In recent times, the specific driver of the lamps brings about an extremely high power factor which, depending on the specific model, lies between 0.85 and 0.93, higher than any other lamp available in the market today. However, due to this high power factor, the lamps hardly cause any reactive power (VAR), a problem that many LED applications still have. Moreover, the lamps consume 80-90% less energy than traditional lamps and even 50% less than average electricity-saving lamps (compact fluorescent lamps, also known as CFL).
Currently, a known problem with light that stems from light emitting diodes is that when the light-intensity of the light emitted by the LEDS is diminished by reason that the level of the current that flows through the LEDS is lowered, the colour of the light does not shift to red in the light-spectrum as it occurs with the lowering of conventional light sources such as light bulbs. Consequently, the light-colour of such dimmed LEDs remains at its original level and subsequently, the light from dimmed LEDs is experienced as being unnatural or even unpleasant to human eye. At some wavelengths (near the color amber) changes of 2-3 nanometres (nm) are discernible to the human eye and at other wavelengths (near the color red) changes of 20-25 nm are required before the human eye can differentiate a color shift. The intensity change with temperature is discernible as well.
Accordingly, there remains a need in the art for light emitting diodes (LEDs) emitting light at a predefined variable light-intensity depending on a level of a feeding-current supplied by a current source.
Accordingly, there exists a need in the art for methods and systems for improving the natural feeling experienced by the human eye when illumination is performed by LEDs, and particularly the LEDs that reduce their level of light-intensity, such that the light that originates from such light emitting diodes shifts to warmer colours, which address the limitations of the prior art.